Field of the Invention
The present invention relates to a fuel cell module including a fuel cell stack formed by stacking a plurality of fuel cells for generating electrical energy by electrochemical reactions of a fuel gas and an oxygen-containing gas.
Description of the Related Art
In general, a solid oxide fuel cell (SOFC) employs a solid electrolyte. The solid electrolyte is an oxide ion conductor such as stabilized zirconia. The solid electrolyte is interposed between an anode and a cathode to form an electrolyte electrode assembly (also referred to as MEA). The electrolyte electrode assembly is sandwiched between separators (bipolar plates). In use, generally, predetermined numbers of the electrolyte electrode assemblies and the separators are stacked together to form a fuel cell stack.
As the fuel gas supplied to the fuel cell, normally, a hydrogen gas produced from hydrocarbon raw material by a reformer has been used. In general, in the reformer, a reforming raw gas is obtained from a hydrocarbon raw fuel of a fossil fuel or the like, such as methane or LNG, and thereafter, the reforming raw gas undergoes partial oxidation reforming, steam reforming, or autothermal reforming, etc. to produce a reformed gas (fuel gas).
In this case, normally, the raw fuel contains sulfur components. If the sulfur components are supplied to the fuel cell, the performance of the fuel cell may be degraded undesirably. Therefore, it is required to remove the sulfur components using a desulfurizer, etc.
For example, a fuel cell power generation system disclosed in Japanese Laid-Open Patent Publication No. 2013-225411 (hereinafter referred to as conventional technique 1) is known. As shown in FIG. 8, this system includes a hydrodesulfurizer 2a for removing sulfur components in a fuel gas added with a reformed gas supplied from a fuel blower 1a. After the sulfur components are removed by the hydrodesulfurizer 2a, the fuel gas is reformed by a reformer 3a. Then, the fuel gas is supplied to a fuel cell main body 4a. A pressure regulator 5a is provided upstream of the fuel blower 1a, for regulating the pressure of the reformed gas supplied from the reformer 3a to the fuel blower 1a. 
Further, a fuel cell system disclosed in Japanese Laid-Open Patent Publication No. 2013-101822 (hereinafter referred to as conventional technique 2) is known. As shown in FIG. 9, the system is equipped with a desulfurizer 1b for removing sulfur components of a raw material gas including hydrogen by hydrodesulfurization. The desulfurized raw material gas after removal of the sulfur components by the desulfurizer 1b is reformed by a first reformer 2b to produce a fuel gas.
A fuel cell 3b receives the fuel gas produced in the first reformer 2b, and generates electrical energy by power generation reactions of the fuel gas and the air supplied from the outside. Further, a second reformer 4b is provided for partially reforming the raw material gas by partial oxidation reaction to produce a partially reformed raw material gas containing hydrogen, and supplying the produced partially reformed raw material gas to the desulfurizer 1b as the raw material gas containing hydrogen.
Further, a hydrogen generator disclosed in International Publication No. WO 2011/077753 (hereinafter referred to as conventional technique 3) is known. As shown in FIG. 10, this hydrogen generator includes a hydrogen generation unit 1c for generating a hydrogen-containing gas using a raw material gas, a hydrodesulfurization unit 2c for removing sulfur compounds in the raw material gas supplied to the hydrogen generation unit 1c, and a recycling channel 3c. The recycling channel 3c supplies the hydrogen-containing gas discharged from the hydrogen generation unit is to the raw material gas in a gas channel 4c upstream of the hydrodesulfurization unit 2c. A raw material gas supply unit 5c is between the hydrodesulfurization unit 2c and a merging section of the gas channel 4c and the recycling channel 3c. 